This is known as 'the Toronto ghost' or 'ghost girl of Toronto'. 
I can't tell if it's a girl ghost, though. Kinda looks like a man in costume to me. 
There is a link on the net which says this has been debunked, but I can't find the debunking itself. 
 
It's not well liked over at YouTube (it's hard to believe what they'll swallow, in terms of a "real" ghost video : ) but I find it intriguing.  
The light traveling across the apparition does not follow the movement of the camera. Now if the companion to the camerawoman happened to be holding a flashlight and shone it on whatever it was, that could explain it, but we have no information. Interestingly, the light does not follow the contour of the apparitions 'body'. This transversely moving light may actually shine through the apparition -- it may be that the app. is somewhat transparent. Unfortunately, with that video quality it's difficult to tell.

Registered